Trifluoromethylcyclohexane derivatives

Abstract

Disclosed are trifluoromethylcyclohexane derivatives of the formula I ##STR1## wherein R is an alkyl or alkenyl radical having up to 18 C atoms which is unsubstituted or substituted by CN or by at least one halogen, and in which one or more non-adjacent CH 2 groups may be replaced by a radical selected from the group comprising --O--, --S--, --CO--, --O--CO--, --CO--O-- and --C.tbd.C--, A 1 and A 2 are each, independently of one another, a) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, b) a 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2 groups may be replaced by --O-- or --S--, c) a 1,4-cyclohexenylene, piperidine-1,4-diyl, 1,4-bicyclo[2,2,2]-octylene or naphthalene-2,6-diyl radical, it being possible for the radicals a) and b) to be monosubstituted or polysubstituted by halogen atoms or cyano and/or methyl groups, ##STR2## Z 1 and Z 2 are each, independently of one another, --CO--O--, --O--CH--, --CH 2 CH 2 --, --CH(CN)--CH 2 --, --CH 2 --CH(CN)--, --CH═CH--, --OCH 2 --, --CH 2 O--, --CH═N--, --N═CH--, --NO═N--, --N═NO--, --N═N-- or a single bond, and o is 0, 1 or 2. These compounds can be used as components of liquid-crystalline media for electrooptical display elements, in particular for matrix liquid-crystal displays.

We claim: 
     
       1. A liquid-crystalline medium having at least two components, wherien one or more component is a trifluoromethylcyclohexane compound of the formula I ##STR92## wherein R is an alkyl or alkenyl radical having up to 18 C atoms which is unsubstituted or substituted by CN or by at least one halogen, and in which one or more non-adjacent CH 2  groups may be replaced by a radical selected from the group comprising --O--, --S--, --CO--, --O--CO--, --CO--O-- and --C.tbd.C--, A 1  and A 2  are each, independently of one another, a) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N,   b) a 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2  groups may be replaced by --O-- or --S--,   c) a 1,4-cyclohexenylene, piperidine-1,4-diyl, 1,4-bicyclo[2,2,2]-octylene or naphthalene-2,6-diyl radical, it being possible for the radicals a) and b) to be monosubstituted or polysubstituted by halogen atoms or cyano and/or methyl groups, ##STR93## Z 1  and Z 2  are each, independently of one another, --CH 2  CH 2  --, --CH(CN)--CH 2  --, --CH 2  --CH(CN)--, --CH═CH--, --OCH 2  --, --CH 2  O--, --CH═N--, --N═CH--, --NO═N--, --N═NO--, --N═N-- or a single bond, and       o is 0or 1.   
     
     
       2. A liquid-crystalline medium according to claim 1, wherein A 1  and A 2  are each, independently of one another, a 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2  groups may be replaced by --O-- or --S--.   
     
     
       3. A liquid-crystalline medium according to claim 1 wherein Z 2  is --CH 2  CH 2  --.   
     
     
       4. A liquid-crystalline medium according to claim 1, containing a compound of the formula I1 ##STR94## in which R, A 1 , ##STR95## Z 1  and o are as defined above. 
     
     
       5. A liquid-crystalline medium according to claim 1, containing a 2-(trifluoromethylcyclohexyl)dioxane compound of the formula I2 ##STR96## wherein R, A 1 , ##STR97## Z 1  and o are as defined above. 
     
     
       6. A liquid crystalline medium according to claim 1 containing a 2-(trifluoromethylcyclo-hexyl)dioxane compound of the formula I2a ##STR98## R is F--(CH2)n--, Cl--(CH2)n--, CH2═CH--(CH2)n--, CmH2m+1--CH═CH--(CH2)n--, CmH2m+1--O--(CH2)n and HC.tbd.CH--(CH2)n and m and n are each independently 0 to 10.   
     
     
       7. A liquid-crystalline medium according to claim 1, containing a trifluoromethylcyclohexane compound wherein the 1,4-cyclohexylene radicals are in the trans-configuration. 
     
     
       8. An electrooptical electrooptical display comprising as a dielectric, a liquid-crystalline medium according to claim 1. 
     
     
       9. A matrix liquid-crystal display comprising as a dielectric, a liquid-crystalline medium according to claim 1. 
     
     
       10. A liquid-crystalline medium according to claim 1, wherein o is 0 or 1.